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A phase-locked loop or phase lock loop (PLL) is a control system that generates an output signal whose phase is fixed relative to the phase of an input signal. Keeping the input and output phase in lockstep also implies keeping the input and output frequencies the same, thus a phase-locked loop can also track an input frequency.
In the classical implementation of a Costas loop, [4] a local voltage-controlled oscillator (VCO) provides quadrature outputs, one to each of two phase detectors, e.g., product detectors. The same phase of the input signal is also applied to both phase detectors, and the output of each phase detector is passed through a low-pass filter. The ...
English: Block diagram of a phase locked loop (PLL), a very common circuit used in radio and telecommunications systems. There are a wide variety of PLL circuits; this diagram shows the simplest type of analog phase locked loop, which functions as a narrow bandwidth filter.
That is, the sequence stays "locked on" to the signal, despite the addition of significant noise to the series θ n. This ability to "lock on" in the presence of noise is central to the utility of the phase-locked loop electronic circuit. [citation needed] There is a mode-locked region for every rational number p / q .
In a traditional phase locked loop (PLL), the frequency divider in the feedback path acts to multiply the phase noise of the reference oscillator and, within the PLL loop bandwidth, impresses this excess noise onto the VCO output.
A phase detector or phase comparator is a frequency mixer, analog multiplier or logic circuit that generates a signal which represents the difference in phase between two signal inputs. The phase detector is an essential element of the phase-locked loop (PLL).
The receiver generates a clock from an approximate frequency reference, and then phase-aligns the clock to the transitions in the data stream with a phase-locked loop (PLL). This is one method of performing a process commonly known as clock and data recovery (CDR). Other methods include the use of a delay-locked loop and oversampling of the ...
Once the frequency is matched, the phase of the carrier must be obtained, or else the demodulated message will be attenuated, but the noise will not be. The local oscillator can be synchronized with the carrier using a phase-locked loop in a synchronous detector arrangement. For SSB, the only solution is to construct a highly stable oscillator.